When password file is used for Redo Transport Authentication, the password of redo transport user should be same across primary and all its physical and snapshot standby databases. By default SYS user is used to authenticate redo transport sessions when password file is used.

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Till 12cR1 Dataguard setup, if there is a change in password file of Primary database like Changes in password or Changes in admin privileges, then the password file needs to be copied from Primary database to standby database server and rename it according to standby database Instance name. If the password file of Primary and Standby databases are not same, then errors will be seen.

In 12cR2, the password file of standby database gets synchronized automatically when there is a change in Primary database password file. The password file change of Primary will be included in Redo and when the Redo is applied to standby, the synchronization happens in the background.

这里延伸几个知识点：

1 、 11g中口令文件并不能实现存放于asm共享访问，修改SYS密码，需要再每个RAC节点手动实施同步 ，同样备库的口令文件也要手动进行更新覆盖
2、12.1版本可以实现口令文件ASM共享存储，RAC中只需要一个节点执行alter user sys 就可以实现主库所有节点同步，这点是11g中无法实现。但是备库中口令文件依然需要手动同步主库的口令文件过来覆盖
3 、12.2版本oracle在口令文件ASM共享存储的前提下，实现了口令文件自动同步主备所有节点

MOS ---
Automatic Password file synchronization in 12.2 Dataguard Standby database

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